The invention relates to a veneer-jointing machine.
In order to produce large-surface veneers from small strips of veneer, these strips must be joined edge to edge. Since veneers are primarily used for furniture, it is desirable to produce veneers with a uniform surface appearance.
The use of taping paper for joining veneer strips has long been known. Strips of kraft paper, provided with glue on one side, serve as taping paper. The taping paper is applied and the veneer strips are joined in so-called veneer joint pasting machines. However, the use of taping paper has proven to be disadvantageous. If the taping paper is located on the outside of the veneer, it must be removed again once the veneer is installed. Taping paper that is applied to the inside of the veneer reduces the bonding strength and, above all, the resistance to moisture of the adhesive bond.
Also known is the use of a glue thread that is placed between the edges to be joined. However this procedure also proves to be problematic because in some cases the glue thread remains visible during the further processing of the veneer.
In order to save the costs for the glue thread or taping paper and to avoid the above-mentioned disadvantages, efforts are made to omit the use of these. A plurality of veneer-jointing machines have been developed, which require neither taping paper nor glue thread. Normally these machines are provided with a large table of metal or wood. The veneer strips to be joined are supplied manually along a holding bar until they are gripped by feed rollers and transferred to the conveying system. The edges of the veneer strips to be joined are coated with glue either prior to the joining, or glue is applied automatically in the veneer-jointing machine. The joint pressure necessary for gluing together the strips is achieved with slanted rollers or a wedge-shaped positioning of the conveying belts.
However, the disadvantage of these machines is that the user is not given the opportunity to produce veneers, which can be fitted together prior to the gluing, so that a desired surface appearance is visible.
German Patent 28 28 901 A1 discloses a device for the fitting together and gluing of veneer strips, with which a plurality of veneer strips can be joined simultaneously. A movable delivery table serves as feeding device, on which the veneer strips are placed side-by-side and ready for assembly in the desired arrangement. The delivery table is inserted into a pressing apparatus, consisting of two pressing plates and one setting device, in which the veneer strips are joined. However, the options of orienting side-by-side arranged veneer strips toward each other are very limited because of the machine design. Also, the above-described apparatus is not suitable for joining veneer strips with a narrow width. German Patent 31 52 554 discloses a device for gluing together plates. In that case, the two plates to be joined are positioned and pushed together by means of two light-barrier controlled conveyor belts. A pasting machine then presses glue under high pressure and with the aid of nozzles into the area to be glued. This device has a complicated design and an observation of the veneer appearance is hardly possible during the joining.
It is the object of the present invention to propose a veneer-jointing machine, which enables the user to join veneer strips with narrow width and, in the process, predetermine the surface appearance as desired.
This object is solved by providing the veneer-jointing machine with a two-part worktable, having a fixed table plate as well as a movable table plate that can be joined to the fixed one, further having a heating device that is arranged above the table plate juncture and can be lowered, a positioning jig that is located below the table plate juncture, opposite the heating device, and can be raised between the table plates, a clamping rail that is arranged above the fixed table plate and is effective in the direction of the table plate, as well as several pressure shoes, arranged side-by-side on the movable table plate, which can be moved at an acute angle to the movable table plate in the direction of the table plate juncture.
Advantageous modifications follow from the claims 2 to 10.
In the starting position, the positioning jig is located between the two table plates. A veneer strip is initially placed on each of the two table plates, in such a way that the pre-pasted edges of the veneer strips fit flush against the positioning jig. The user then can move these strips parallel to each other along the positioning jig until the desired surface appearance is visible. The veneer strips are then secured with the clamping rail and the pressure shoes, the positioning jig is lowered, and the movable table plate is moved in the direction of the fixed table plate, until the edges of the veneer strips adjoin. Since the pressure shoes can be moved at an acute angle to the movable table plate, in the direction of the table plate juncture, these pressure shoes can be used to additionally press the veneer strip on the movable table plate against the second veneer strip. The joint pressure can thus be increased and any unevenness in the veneer strip edges can be compensated.
The heating device is subsequently lowered and the glue applied to the edges is heated with this device. Following a predetermined interval, the heating device is moved back to the starting position, the glue hardens and joins the two veneer strips.
Prior to removing the veneer, the pressure shoes and the clamping rail are released. As soon as the movable table plate has returned to its starting position and the positioning jig between the table plates is raised, the following veneer strips can be inserted.
The veneer-jointing machine according to the invention allows the user to exactly predetermine the surface appearance of the veneer by displacing the veneer strips along the positioning jig. The device according to the invention also permits joining veneer strips with narrow widths and even veneer strips of varied lengths and widths.
It is advantageous if the movable table plate can be moved with the aid of a first lifting cylinder, by means of a first piston. For this, pneumatic or even hydraulic lifting cylinders can be used, which are available in a plurality of different embodiments. The lifting cylinder can move the movable table plate to the exact, predetermined position and without force expenditure by the user.
It is advantageous if the heating device can be lowered with the aid of a second lifting cylinder and via a second piston.
The heating device preferably comprises a heating cartridge with an electrical resistor element, with which the necessary temperature can be adjusted precisely.
It is advantageous if the positioning jig can be lifted with a third lifting cylinder and via a third piston.
The positioning jig preferably comprises a thin, upward pointing blade. At the start of the process, this blade is positioned between the table plates and projects somewhat over these plates. The veneer strips, which are arranged tightly joined and side-by-side, can be oriented toward each other without problems along this blade.
The use of a fourth lifting cylinder and a fourth piston recommends itself for the operation of the clamping rail.
The clamping rail preferably can be tilted around a shaft, relative to the fixed table plate. In this way, it is possible to exactly meter out the pressure the clamping rail exerts on the veneer strips positioned on the table plate.
It is advantageous if the pressure shoes are each arranged inside a guide of a cylinder, such that they can be adjusted.
It is possible to activate the pressure shoes jointly as well as separately. If the pressure exerted by these in the direction of the table plate can be adjusted separately for each pressure shoe, it is possible to compensate exactly for uneven edges of the veneer strips.
One advantageous design of the veneer-jointing machine is provided with a central control for coordinating the individual process steps in order to simplify and accelerate the production process. Thus, after the veneer strips are inserted and oriented, the following process steps are executed automatically by pushing a button.